In some medical procedures, such as those to treat conditions in the upper urinary tract of a patient, medical instruments must be inserted into the body of the patient and positioned at a target site within the patient's body. In some procedures, an endoscope, such as a cystoscope, is first introduced into the bladder of the patient. A guidewire or another medical instrument then is introduced into the patient's body through the cystoscope. The guidewire is passed through a working channel of the cystoscope until the distal or insertion end of the guidewire exits the distal end of the cystoscope and enters the bladder of the patient. The advancing distal end of the guidewire must then somehow be directed to the target location, such as to and through the entrance of the patient's ureter. Directing the guidewire into the patient's ureter with known techniques and tools often proves difficult.